Five years after enactment of the Affordable Care Act, the political debate between its supporters and its opponents continues to rage with remarkably little change.

But the success of the law in extending insurance coverage to millions of Americans could dramatically change the terms of that debate if either the latest congressional Republican legislative assaults or a pending Supreme Court case threatens its future, enabling the Democrats to regain the offensive for the first time since the law was passed.

Predictable statements from both sides marked the law’s recent anniversary.

President Barack Obama and his Democratic allies used the occasion to cite the increasing statistical evidence that the landmark measure has succeeded in sharply reducing the number of Americans without health care coverage, slowing the growth rate of health care costs and proving less costly than even some backers had feared.

In those five years, the White House says, 16.4 million Americans have gained health insurance, reducing the percentage of uninsured Americans from 20.3 percent to 12.9 percent and the law’s projected 10-year cost by some $116 billion.

Republican critics, meanwhile, continue to denounce Obamacare as unworkable and costly. And they’re using their new congressional majorities to plot its destruction via the same legislative procedure the Democrats used to pass it while hoping the high court will help them by ruling out a key element in financing it.

Critics claim that the law has increased average deductibles by 40 percent for families, cost many people their existing insurance and imposed tax increases that have helped to slow the economic recovery from the Great Recession.

Last week, both House and Senate passed budgets that included provisions directing their legislative committees to draft measures to repeal the law. They plan to include it in the reconciliation measure that would implement their budget, since the Senate’s GOP majority can pass that without fear of a Democratic filibuster.

But the fate of any legislative challenge remains questionable as long as President Obama is in office, prepared to wield his veto pen. Meanwhile, supporters of the law are more concerned about the pending Supreme Court case challenging the validity of tax credits for more than 7.5 million people who purchased health insurance from the federal government’s exchange, rather than from ones operated in 13 states.

Some congressional Republicans have indicated that, if the court sides with the challenge, they would press forward with an alternative to the Affordable Care Act that would preserve such popular features as the protection against being denied coverage because of pre-existing conditions and raising the age for letting young people remain on their parents’ insurance plans.

In any case, if either legislation or the Supreme Court cripples the law, and Congress fails to restore its principal provisions, the resulting debate could focus less on the merits of the law than on the impact of the loss of benefits for many of its 16 million beneficiaries, who have gained access to insurance or received expanded Medicaid benefits from many states.

That, in turn, could give the Democrats the political high ground they lacked as long as the debate centered on enactment of a law that a majority of Americans opposed. That’s because recent polls show only a minority wants to scrap it while a majority wants Congress and the Obama administration to find ways to fix its flaws.

But the prospect of a changed political climate shows no sign of stopping either the array of Republican presidential hopefuls vowing to repeal the law in 2017 or the congressional Republicans from proceeding against it now.